Offset printing machine with wiping sheet for removing ink from blanket cylinder



Aug. 26, 1969 H. KUFEIQ 3,463,082

OFFSET PRINTING MACHINE WITH WIPING SHEET FOR REMOVING INK FROM BLANKETCYLINDER Filed April 5,' 1966 3 Sheets-Sheet 1 Fig] ,8a 18. 79 2] i 772069a -O 20a L /9 o 23 a 33 9.25 seb 3359 31a 336 `4 sbgbovw' I W13?7erir l L39 R I 4g l Il, I 24e 36e m4 2% m 2 4l \l \\`30 36d 7 a f '0l3.23.1 43 .38 ,4d 24a 4 24h 9b \;`2\92 73 l ,l 9 27 l 23 29 42 z: f

IN V EN TOR.

HELMUT KUFER Aug. 26, 1969 H. KUFf-:R 3,453L032 OFFSET PRINTING MACHINEWTH WPING SHEET FOR REMOVING v INK FROM BJANKFT CYLINDER Filed Aprilia,1966 5 Sheets-Sheet 2 INVENTOR.

HELMUT KAUFER Aug. 26, 1969 H, KUFER 3,463,082

OFFSET PRINTING MACHINE WITH wIPING SHEET FOR REMOVING INK FROM BLANKETCYLINDER Filed April 5, 1966 3 'Sheets-Sheet 3 INVENTOR.

H11-LMU? KUFER BY Mum! ff/iw United States Patent O 3,463,082 FFSETPRINTING MACHINE WITH WIPING SHEET FOR REMOVING INK FROM BLAN- KETCYLINDER Helmut Kufer, Metzkausen/uber Mettmann, Germany,

assigner to Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany FiledApr. 5, 1966, Ser. No. 540,291 Claims priority, application Germany,Apr. 15, 1965,

rat. Cl. B411? 9/08, 13/24 U.S. Cl. lill-144 18 Claims ABSTRACT F THEDISCLOSURE The present invention relates to offset printing machines ingeneral, and more particularly to improvements in cleaning or wipingdevices for removing ink from the blanket of the rubber blanket cylinderin an offset printing machine. Still more particularly, the inventionrelates to improvements in wiping or cleaning devices for rubber blanketcylinders which are especially suited for use in comparatively smalloffset printing machines of the type normally employed in oices andsimilarestablishments to produce relatively small numbers or stacks ofprinted copies.

It is well known that the blanket of the rubber blanket cylinder in anoffset printing machine must be cleaned to remove remaining ink prior toinsertion of a 'fresh master sheet. Proper cleaning of the blanket takesup considerable time; in fact, such cleaning can take up an interval oftime which is a multiple of the time required to produce a relativelysmall number of printed copies.

Accordingly, it is an important object of the present invention toprovide an improved offset printing machine wherein the removal of inkfrom the exposed surface of the blanket of a rubber blanket cylinderrequires very little time and wherein such removal can take placeimmediately after the printing operation is completed so that the stillwet or moist ink can be removed without resorting to solvents.

Another object of the invention is to provide the improved machine witha novel foil which can be used as a master sheet, as a wiping device forthe blanket, and as a back support for fresh copy sheets during actualprinting.

A further object of the invention is to provide the improved offsetprinting machine with a foil of the just outlined characteristics and toprovide the foil with very simple and reliable anchoring means tofacilitate its attachment to or disconnection from suitable clampingdevices on the master cylinder of the machine.

An additional object of the instant invention is to provide the offsetprinting machine with a very simple but reliable and compact controlunit which can be readily manipulated by semiskilled persons and whichcan convert the machine from printing to wiping or vice versa.

A concomitant object of the invention is to provide the offset printingmachine with a novel master cylinder which, in addition to being capableof transferring ink to the blanket, is also capable of carrying a wipingde- Mice vice for the blanket and of serving as a back support for freshcopy s'heets during printing.

Still another object of the invention is to provide the machine with awiping device for the blanket of the rubber blanket cylinder and toconstruct and mount the wiping device in such a way that it can alsoperform at least one additional important function, particularly ofserving as a back support for fresh copy sheets during actual printingor as a back support during writing or otherwise applying images to themaster sheet.

A further object of the invention is to provide an offset printingmachine wherein the wiping device for the blllanket can be caused toswitch places with the master s eet.

Brieily stated, one feature of my invention resides in the provision ofan offset printing machine which cornprises a rotary rubber blanketcylinder, a rotary master cylinder and platen unit which may comprise asingle cylinder or a separate master cylinder and a separate platencylinder and whose purpose is to respectively transfer inked images toand to constitute a back support for the blanket cylinder, animage-transferring master sheet, a cleaning or wiping sheet for removingink from the blanket of the blanket cylinder, and clamping meansdetachably securing the sheets to the aforementioned unit.

In accordance with a more specific feature of my invention, the unit cancomprise a single cylinder and the clamping means then comprises twoclamping devices provided on such single cylinder. The two sheets arethen preferably combined into a single foil which can be applied aroundthe periphery of the single cylinder in such a way that both sheetsremain exposed or that one of the sheets is withdrawn into the interiorof the single cylinder when the other sheet is exposed or vice versa.The machine further preferably comprises suitable control meansincluding selector means for moving the blanket cylinder into contactwith the one or the other sheet, depending upon whether the machine isset for printing or for cleaning of the blanket on the blanket cylinder.The wiping sheet may also serve as a back support for fresh copy sheetsat the time such copy sheets are being fed into and pass through thebite between the blanket cylinder and the cylinder which carries thewiping sheet.

Alternatively, the machine may comprise a unit which is composed of twocylinders, namely a master cylinder which carries the master sheet and aplaten cylinder which carries the wiping sheet. When the machine is inactual use to print images on copy sheets, the blanket receives inkedimages from the master sheet and the platen cylinder (and moreparticularly the wiping sheet thereon) serves as a back support for suchfresh copy sheets. In order to clean the blanket, the master sheet ismoved away from contact with the blanket and the feed of fresh copysheets is interrupted so that the wiping sheet automatically removes allsurplus ink from the exposed surface of the blanket.

The novel features which are considered as characteristic of theinvention are aet forth in particular in the appended claims. Theimproved offset printing machine itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of certain specific embodiments withreference to the accompanying drawings, in which:

FIG. l is a partly elevational and partly vertical sectional view of anoffset printing which embodies one form of my invention, the sectionbeing taken in the direction of arrows as seen from the line I-I of FIG.2;

FIG. 2 is a fragmentary horizontal section substantially 3 as seen inthe direction of arrows from the line II-II of FIG. 1;

FIG. 3 is a fragmentary vertical section through a portion of a modifiedoffset printing machine wherein the wiping sheet is carried by a platencylinder;

FIG. 4 is a transverse section through a master cylinder which isprovided with means for selectively exposing the master sheet or thewiping sheet;

FIG. 5 is a similar transverse section through a further master cylinderand illustrates the foil prior to attachment of the master sheet to thecorresponding clamping device;

FIG. 6 is a similar section and illustrates the foil in fully appliedposition with the master sheet exposed; and

FIG. 7 is a similar section but showing the wiping sheet in exposedposition.

Referring irst to FIGS. l and 2, there is shown an off* set printingmachine comprising a frame 1 which supports a rotary shaft 2 for a unitincluding a single combined master, cleaning or wiping and platencylinder 4, hereinafter called master cylinder. A diametral pin 3connects the master cylinder with the shaft 2 so that the parts 2 and 4rotate as a unit. The master cylinder 4 is provided with clampingdevices 5 and 6 for a combined master and wiping or cleaning foil 7, thelatter being applied around the periphery of the master cylinder andbeing composed of two portions or sheets 7a and 7b. The master sheet 7ais indicated by broken lines and its impression surface serves as acarrier of the image which is to be transferred to the rubber blanket 12of a second or rubber blanket cylinder 11. The sheet 7b serves as acleaning or wiping device and is indicated by a corrugated or undulateline because its exposed surface is rather rough. The clamping devices 5and 6 may be of the well known type, for example, each such clampingdevice may comprise a spring biased anchor bar which is provided withhooked projections extending into openings provided therefor in thescalloped edge portions of the sheet 7a and 7b. It will be noted thatthe clamping devices 5 and 6 are accommodated in a recess provided inthe periphery of and extending in parallelism with the axis of themaster cylinder 4. The length of the foil 7 and the combined width ofclamping devices 5, 6 together approximate the circumferential length ofthe cylinder 4.

The frame 1 further supports a second shaft 8 which is parallel with theshaft 2 and carries one end of each of two rocker arms or holders 9whose other ends carry the shaft 10 of the rubber blanket cylinder 11.The latter carries the aforementioned blanket 12 whose edges are held bysuitable clamping devices of known design. As shown in FIG. l, theblanket 12 is wrapped around the cylinder 11 and its clamped edgeportions extend into an axially parallel recess provided in theperiphery of the cylinder 11. The diameter of the rubber blanketcylinder 11 equals half the diameter of the master cylinder 4. Theholders 9 are biased by springs 13 which tend to rock them in acounter-clockwise direction, as viewed in FIG. 1, so that the blanket 12is normally urged against the foil 7 on the cylinder 4. FIG. 1 merelyshows one of the holders 9 and a single spring 13.

One end face of the cylinder 4 carries a specially congurated face cam14 whose endless cam groove comprises a first arcuate portion 14a whichis more remote from the shaft 2 and a second arcuate portion 14b whichis nearer to the shaft 2. The cam 14 forms part of a control assembly.The two cam groove portions 14a, 14b are connected with each other bytwo intermediate groove portions 14C, 14d which serve to guide apin-shaped follower 15 in such a way that the latter can rapidly movefrom the groove portion 14a into the groove portion 14b or vice versawithout being subjected to excessive shocks. The cam groove portions 14aand 14b are respectively coextensive (more or less) with the sheets 7aand 7b of the foil 7 on the master cylinder 4. As stated before, theconfiguration of the intermediate cam groove portions 14C, 14d is suchthat the follower 15 can rapidly advance from the groove portion 14a tothe groove portion 14b or vice versa, i.e., in response to a relativelysmall angular displacement of the master cylinder 4.

A third shaft 14, fixed to the frame 1, supports a roller-shapedapplicator 17 which forms part of an inking unit and serves as a meansfor distributing coloring matter (hereinafter called ink for short)along the periphery of a coating or inking roller 21 which can come indirect contact with the master sheet 7a. The applicator 17 can receiveink from a withdrawing roller 18 through the intermediary of a rockableductor roller 19 mounted on a rocker arm 19a. The ductor roller 19 islocated in the space between the applicator 17 and withdrawing roller18, and the latter is driven to withdraw ink from a fountain or source18a. The rate at which the ductor roller 19 can transfer ink from thewithdrawing roller 18 to the applicator 17 is adjustable in a manner notforming part of the present invention. The applicator 17 is in rollingcontact with a moistening or wetting roller 33 which forms part of awetting unit and draws a film of liquid from a source or tank 32 toapply such film of liquid over the layer of ink which is transferred bythe ductor roller 19. The shaft 16 for the applicator 17 supports twoswingable levers or carriers 20 (only one shown in FIG. l) which areprovided with aligned elongated slots 20a for the shaft of the inkingroller 21 so that the latter can reciprocate toward and away from theshaft 16. The shaft of the inking roller 21 is biased by springs 22which maintain the periphery of the inking roller 21 in permanentcontact with the periphery of the applicator 17. The free ends of thecarriers 20 are biased by springs 23 which tend to maintain the inkingroller 21 in permanent rolling contact with the master sheet 7 on thecylinder 4.

The follower 15 is mounted on a motion transmitting lever 24 which isrockable on a pin 25 fixed to the frame 1. This motion transmittinglever 24 is coupled with a push rod 26 by means of a pivot pin 26a whichextends through a lug 24a of the lever 24. The push rod 26 is alsocoupled with a rockable lever or link 69 having a projection 69aengaging one of the carriers 20 and serving to move the inking roller 21away from the master cylinder 4 as soon as the follower 15 enters thecam groove portion 14a, i.e., as soon as the wiping sheet 7b travelsbelow the inking roller. In this way, the push rod 26 and link 69prevent transfer of ink to the wiping sheet 7b.

The lever 24 is provided with two cam faces 24b, 24e which are disposedat the opposite sides of the pivot pin 25 and each of which can beengaged by the free end of a regulating link 27 forming part of aselector unit and being pivotally connected with an intermediate portionof one of the holders 9. The selector unit further comprises aconnecting link 28 which is articulately coupled to an intermediateportion of the regulating link 27 and to one arm 29a of a three-armedselector lever 29 rockable on a frame-supported pin 30. Another arm 31of the selector lever 29 has a knob-like index 31a which can be moved byhand into registry with one of a series of graduations D, V, N and Rprovided on the frame 1. Furthermore, the index 31a is slidable in anarcuate guide slot 31b of the frame 1. In the illustrated position, theindex 31a registers with the graduation V which means that the machineis set for preinking of the master sheet 7a. The regulating link 27engages the cam face 24o of the motion transmitting lever 24. Therefore,the blanket 12 of the cylinder 11 will move into contact with the mastersheet 7a of the foil 7 during each revolution of the master cylinder 4.Also, the blanket 12 will move away from the wiping sheet 7b during eachrevolution of the master cylinder 4. On the other hand, the inkingroller 21 moves into engagement with the master sheet 7a during eachrevolution of the master cylinder 4 so that the image on the sheet 7atransfers ink to the exposed surface of the blanket 12 during eachrevolution of the master cylinder 4. In other words, all of the symbolscarried by the sheet 7a are reproduced on the exposed surface of theblanket 12.

The frame 1 further supports two guide pins 34, 35 which extend intoelongated guide slots 36a, 36b of a slide 36 forming part of a feedunit. The slide 36 is biased by a spring 37 which tends to move it in adirection to the left, as viewed in FIG. 1. A guide 36C of the slide 36accommodates a portion of a reciprocable arm 36d also forming part ofthe sheet feeding unit which latter further comprises a sheet advancingor feeding roll 38. A pusher or trip 39 carried by the right-handportion of the slide 36 can engage the arm 24d of the motiontransmitting lever 24. The trip 39 is mounted on a pivot pin 40 of theslide 36 and is rockable about the pin 40 by a link 41 which isarticulately coupled to the arm 29h of the selector lever 29.

If the index 31a of the selector lever 29 is moved into registry withthe graduation D on the frame 1, the machine is set for printing. Thetrip 39 then engages the arm 24d of the motion transmitting lever 24and, at the same time, the regulating link 27 is rocked in a clockwisedirection, as viewed in FIG. 1, and moves beyond (to the right of) thecam face 24C. Therefore, the blanket 12 of the cylinder 11 remains incontinuous contact with the foil 7, i.e., not only with the master sheet7a but also with the wiping sheet 7b. Also, and since the trip 39 on theslide 36 engages the arm 24d of the motion transmitting lever 24, theslide 36 is caused to move in a direction to the right whenever thelever 24 is rocked in a clockwise direction, i.e., whenever the follower15 moves from the cam groove portion 14a into the cam groove portion14b. Therefore, the advancing roll 38 shifts the topmost copy sheet 43of the stack on the supporting platform or table 42 in a direction tothe right and advances such topmost sheet into the bite between thecylinders 4 and 11, namely, between the foil 7 and blanket 12. In suchposition of the index 31a, the wiping sheet 7b merely serves as a platenor back support for fresh copy sheets 43 during printing. The blanket 12transfers printed matter to the underside of the thus advanced copysheet 43 and thereupon advances the properly imprinted copy sheet into areceiving rack or collector here shown as an inclined tray 44.

When the follower 15 moves from the cam groove portion 14b into the camgroove portion 14a, the motion transmitting lever 24 is rocked in acounterclockwise direction, as viewed in FIG. 1, whereby the spring 37is free to retract the slide 36 in a direction to the left and back toits starting position. The slide 36 remains in such starting positionduring the entire interval in the course of which the follower 15travels in the ca-m groove por tion 14a. Thus, no copy sheet 43 can befed during such interval so that the blanket 12 on the cylinder 11 canroll along the master sheet 7a and the latter applies thereto ink toreplace ink which was removed during printing of the preceding copysheet.

If the inking of the blanket 12 and the production of printed copysheets 43a is to be terminated or interrupted, the index 31a will beshifted into registry with the graduation N whereby the regulating link27 engages a median cam face 24e of the lever 24 which is locatedbetween the cam faces 24b, 24C. The position of the cam face 24e is suchthat its portions perform negligible radial movements with reference tothe pin 25 when the motion transmitting lever 24 is rocked in responseto travel of the follower 15 in the composite cam groove of the face cam14. The distance between the cam face 24e and the pin 25 is selected insuch a way that, when the cam face 24e is engaged by the upper endportion of the regulating link 27, the latter holds the blanket 12 outof contact with the foil 7, i.e., the holder 9 is rocked in acounterclockwise direction. At the same time, the arm 29h of theselector lever lifts the link 41 so that the latter maintains the trip39 out of contact with the arm 24d of the lever 24 whereby the slide 36remains in its starting position and the roll 38 cannot feed fresh copysheets 43 into the bite between the cylinders 4 and 11.

If the operator moves the index 31a into registry with the graduation R(wiping or cleaning), the regulating link 27 is moved into engagementwith the cam face 24b of the lever 24. Consequently, the blanket 12 ismoved away from the foil 7 (master sheet 7a) when the follower 15 entersthe cam groove portion 14a but will engage the wiping sheet 7b when thefollower 15 enters the cam groove portion 14h. In other words, duringeach revolution of the master cylinder 4, the blanket 12 comes intorolling Contact with the wiping sheet 7b but not with the master sheet'7a. When the index 31a is shifted from registry with the graduation Ninto registry with the graduation R, the trip 39 is rocked in aclockwise direction, as viewed in FIG. l, and moves even farther awayfrom the arm 24d of the lever 24 so that the feed unit including theslide 36 and roll 38 remains idle. As the master cylinder 4 continues torotate, all remaining ink on the exposed surface of the blanket 12 israpidly transferred onto the exposed surface of the wiping sheet 7b sothat the blanket 12 is rapidly cleaned.

FIG. 2 shows that the front end portion of the shaft 2 for the mastercylinder 4 extends beyond the frame 1 and carries a manually operablemanipulating member in the form of a hand wheel 45 which is securedthereto by a radial pin 46, A screw 47 serves to hold the hand wheel 45`against excessive axial movement away from the shaft 2. The pin 46extends into and is slidable in an axially parallel peripheral groove 2aof the shaft 2. The hand wheel 45 has some freedom of axial move-mentwith reference to the shaft 2 and is biased in a direction toward theframe 1 by a corrugated annular dished spring 47 interposed between thehead of the screw 47 and the hub of the hand wheel. This hub carries afirst clawed clutch element 45a which is biased by the spring 48 intomotion receiving engagement with a complementary clawed clutch element50a provided on a gear 50, the latter being rotatably supported by theshaft 2 between the frame 1 and the adjoining end portion of the mastercylinder 4. The gear 50 serves to provide a driving connection betweenthe cylinders 4, 11 and its teeth 50b mesh with the teeth of :acomplementary driver gear (not shown) on the shaft lll of the cylinder11 to insure that the two cylinders rotate at the same peripheral speed.The diameter of the pitch circle of the gear 50 equals the diameter ofthe master cylinder 4, and the same holds true for the driver gear andcylinder 11. If the operator decides to pull the hand wheel 45 `againstthe bias of the spring 43, i.e., in a direction indicated in FIG. 2 byarrow A, the clutch elements 45a, 50a are disengaged from each other andthe driving connection between the cylinders 4, 11 is terminated. Thehand wheel 45 can be utilized to change the angular position of themaster cylinder 4 with reference to the cylinder 11 so that the operatorcan readily move different portions of the wiping sheet 7b into contactwith different portions of the exposed surface on the blanket 12 tothereby insure complete removal of ink from the blanket. For example,the cylinder 11 may be rotated at a constant speed by a drive includingan electric motor or another suitable prime mover, :and the operatorwill manipulate the hand wheel 45 to respectively disengage and reengagethe gear 50 with the driver gear on the shaft 10, such reengagementtaking place subsequent to angular displacement of the cylinder 4 withreference to the cylinder 11. Actually, the operator must only pull thehand wheel 45 in the direction of the arrow A because the angularposition of the cylinder 11 (which is driven) changes automatically assoon as the clutch including the elements 45a, 50a is renderedineffective. Also, the person in charge need not fear that he wouldaccidentally reengage the cylinders 4, 11 in an angular position inwhich the blanket 12 would come into contact with the master Sheet 7abecause the follower 15 remains in the groove of the cam 14 and thusautomatically prevents direct contact between the sheet 7a and blanket12. The same holds true for the inking roller 21 which is invariablylifted away from the cylinder 4 as soon as the follower 1S leaves thecam groove portion 14b to enter the cam groove portion 14a.

A very important advantage of the machine shown in FIGS. l and 2 is thatcleaning or wiping of the blanket 12 requires very little time and alsothat the wiping sheet 7b can be reused as often as desired, i.e., aslong as the foil 7 remains attached to the master cylinder 4. All thatan operator has to do is to shift the selector lever 29 to a position inwhich the index 31a registers with the graduation R and the wipingoperation proceeds in a fully automatic way while the feed of fresh copysheets 43 and the transfer of ink to the master sheet 7a remaininterrupted. The selector lever 29 may be shifted while the machine isin actual use so that the transition from printing to wiping or viceversa can be effected without necessitating any manipulation of controlelements which start or arrest the prime mover of the machine. Thewiping sheet 7b is expendable and may be produced at low cost lbecauseit need not meet any special requirements excepting that it should becapable of collecting ink which remains on the exposed surface of theblanket 12. Thus, whenever the master sheet 7a is to be discarded orreplaced by another master sheet, the wiping sheet 7b is discarded withthe master sheet. Due to the fact that the improved machine canaccommodate a foil 7 which in part serves as a master sheet and in partas a wiping sheet for the blanket 12, the machine need not be equippedwith any other cleaning or wiping devices so that its dimensions may bereduced considerably. Furthermore, and since the cleaning or wipingoperation can begin as soon as the printing of a selected number offresh copy sheets 43 is completed, the wiping sheet 7b can remove inkwhich is still wet or moist so that such removal can take place withoutresorting to solvents which are necessary in many presently known typesof Offset printing machines wherein ink remaining on the blanket isallowed to harden. All that is necessary is to construct the controlsystem of the machine (including the drive for the cylinders 4, 11 andthe assembly of levers, links, slides, trips and similar elements shownin FIGS. 1 and 2) in such a way that the wiping operation can be startedimmediately following completion of a printing operation. Thus, all thatis necessary is to control movements of the cylinder 11 toward and awayfrom the foil 7 in such a way that the cylinder 11 can move intorepeated contact with the wiping sheet 7b but is held out of contactwith the master sheet 7a. It is further clear that the length of thewiping sheet 7b need not equal the length of the master sheet 7a.However, it is advisable to utilize a wiping sheet having a certainminimum length in order to make sure that the material of the wipingsheet can remove all such ink which remains on the blanket 12 uponcompleted printing of crowded images onto copy sheets 43, i.e., When theimage transferred onto the blanket 12 occupies a substantial percentageof its exposed surface.

The fact that the wiping sheet 7b can serve as a back support for theblanket 12 when the latter transfers an image onto a freshly admittedcopy sheet 43 is not detrimental for the quality of prints. As a matterof fact, and since the material of the wiping sheet 7b is preferably offelt-like consistency, this wiping sheet constitutes a more satisfactoryback support than a metallic body such as is employed in many presentlyknown small offset printing machines.

The effective length of the wiping sheet 7b is shown as being at leastequal to the effective length of the master sheet 7a, i.e., the wipingsheet can be brought into ink removing contact with all such portions ofthe blanket 12 which come into contact with the master sheet. Therefore,it normally suffices to bring the 'blanket 12 into repeated rollingcontact with the sheet 7b whereby the latter reliably removes allsurplus ink from the exposed surface of the blanket, especially if thewiping action follows the printing operation without delay. The manuallyoperable wheel 45 will be manipulated only as a precautionary measure orwhen the operator notes that some ink continues to adhere to the blanket12 after the cylinders 4, 11 have performed several revolutionssubsequent to movement of the index 31a into registry with thegraduation R.

In the event that the improved offset printing machine comprises aseparate platen cylinder, i.e., that the wiping sheet 7b need not act asa back support, a cleaning action between the exposed surface of thewiping sheet 7b and the exposed surface of the blanket can be achievedby constructing the master cylinder 4 in such a way that the portion ofthis cylinder which carries the sheet 7b has a different radius thanthat of the pitch circle of the gear 50. The difference between the tworadii equals the thickness of the sheet 7b. In such a modified machine,the platen cylinder will be rocked to operative position and the feedunit will Ibe rendered operative when the index 31a registers with thegraduation V. The cleaning or wiping operation will take place when theindex 31a registers with the graduation R.

FIG. 3 illustrates a portion of a further offset printing machine whichcomprises a rubber blanket cylinder 63 and a platen cylinder or backsupport 64. The latter is provided with two releasable clamping devices65, 66 for a wiping sheet 67 which surrounds the major part of theperipheral surface of the cylinder 64. This cylinder 64 is also formedwith a recess or cutout which extends between the clamping devices 65,66 and accommodates a conventional paper gripper 68. FIG. l shows thatthe cylinder 11 carries a similar gripper. The gripper 68 of FIG. 3 isrockable in synchronism with rotation of the cylinder 64 and withoperation of the feed unit so that it can grip the leading edge of thetopmost fresh copy sheet 43 when the latter is advanced from the table42 by the feed roll 38. For example, the gripper 63 may be permanentlybiased by a spring and may be controlled by a suitable fixed cam in amanner well known from the art of offset printing machines. Its purposeis to draw the copy sheets 43 through the bite between the cylinders 63,64 and to release each freshly printed sheet 43a in good time so thatsuch printed sheets 43a can accumulate in the tray 4-4.

When the nking of the blanket 63a on the cylinder 63 and the feed offresh copy sheets 43 is interrupted in a manner as described inconnection with FIGS. 1 and 2, the remaining ink may be rapidly removedfrom the exposed surface of the blanket 63a by repeated contact with theexposed surface of the wiping sheet 67. Such removal of remaining inkcan be completed in response to a few revolutions of the cylinders 63,64.

The cleaning or wiping effect may be improved considerably if the shaft64a of the platen cylinder 64 carries a clutch which can be disengagedby a readily accessible hand wheel similar to the hand wheel 45 of FIGS.l and 2 in order to change the angular position of the cylinder 64 withreference to the cylinder 63. The two cylinders are normally coupled forrotation at the same peripheral speed and the just mentioned clutchenables the operator to change the angular position of the cylinder 64by equal or nearly equal increments to move different surface portionsof the blanket 63a into contact with different portions of the exposedsurface on the wiping sheet 67. The cylinder 63 may be driven at aconstant speed by a drive including an electric motor, a hand crank oranother suitable prime mover.

In order to avoid damage to the blanket 63a, the recess between theclamping devices 65, 66 should be deep enough to accommodate the gripper68 in each of the latters angular positions, i.e., this gripper 68should not extend beyond the outline of the cylinder 64. It is equallypossible to provide a control system which automatically increases thethe distance between the cylinders 63, 64 when the gripper 68 approachesthe blanket 63a. Itis further important to ultimately recouple thecylinders 63, 64 in such angular positions that the operation of thegripper 68 is again synchronized with the operation of the feed unitincluding the advancing roll 38. This can be readily achieved byresorting to a conventional one-tooth clutch which insures accurateengagement of its elements only when the cylinders 63, 64 are moved todesired angular positions with reference to each other.

Otherwise, the operation of the offset printing machine shown in FIG. 3is analogous to that of the previously described machines. Of course,the master cylinder of this machine need not carry a wiping sheet 7b. Avery irnportant advantage of the embodiment shown in FIG. 3 is that thewiping sheet 67 can constitute an exceptionally satisfactory backsupport for the copy sheets 43 which are being fed into the bite betweenthe cylinders 63, 64. Also, the cleaning or wiping operation can beinitiated in a very simple and time-saving manner. All that is necessaryis to interrupt the feed of fresh copy sheets 43 whereby the exposedsurface of the blanket 63a is free to come in direct Contact with thewiping sheet 67.

FIG. 4 shows a further master cylinder 52 which can replace the mastercylinder 4 of FIGS. l and 2. This master cylinder carries a modifiedfoil 7 having a master sheet 7a and a wiping or cleaning sheet 7b. Theinterior of the cylinder 52 is hollow and accommodates two clampingdevices in the form of collecting drums or reels 5l, 53. The drum 51 isprovided with an axially parallel peripheral clamping groove 51a whichreceives and retains one edge portion of the wiping sheet 7b. Theaxially parallel peripheral clamping groove 53a of the drum 53 receivesand retains one edge portion of the master sheet 7a. The drum 53 isnormally held against rotation in one direction (namely, in a directionto pay out the master sheet 7a') by a one-way clutch including a ratchetwheel 54 and a pawl 55. A similar one-way clutch including a ratchetwheel 56 and a pawl 57 holds the drum 51 against rotation in a sense topay out the wiping sheet 7b'. ln the illustrated position, the wipingsheet 7b extends along the entire circumference of the master cylinder52. If the master sheet 7a is to be moved to operative position, theoperator disengages the pawl 55 from the ratchet wheel 54 and the drum51 is rotated by means of a knob or the like (not shown) in a sense tocollect the wiping sheet 7b whereby the latter unwinds the master sheet7a and causes it to surround the periphery of the drum 52. In otherwords, in order to switch from transfer of ink from the master sheet 7a'to the non-illustrated blanket over to cleaning of the blanket by meansof the wiping sheet 7b' or vice versa, the operator manipulates theone-way clutch 54, 55 or 56, 57 and thereupon rotates the drum 51 or 53in a sense to collect the sheet 7a or the sheet 7b. While the solutionshown in FIG. 4 requires additional manual work, it brings aboutconsiderable simplification of the control arrangement in the offsetprinting machine because the rubber blanket cylinder need not be movedaway from the master cylinder 52.

The diameter of the master cylinder S2 can be the same as that of thecooperating rubber blanket cylinder, not shown. The machine whichembodies the master cylinder 52 need not be provided with a specialcontrol system. All that is needed to start a cleaning operation is toarrest the drive and to thereupon manipulate the one-way clutch 54, 55so that the wiping sheet 7b can be moved to operative position asactually shown in FIG. 4, i.e., that the wiping sheet surrounds thecylinder 52. The drive is thereupon started anew and the cleaningoperation begins in a fully automatic way. It is clear that the drivingconnection between the blanket cylinder and the master cylinder 52 ofFIG. 4 can also include a manually engageable or disengageable clutch toallow for placing selected portions of the wiping sheet 7b into contactwith selected portions of the blanket in the same way as described inconnection CTI l0 with the clutch 45a, 50a of FIG. 2. The prime mover ofthe machine is preferably coupled with the blanket cylinder and theaforementioned clutch transmits rotary motion to the master cylinder 52.

Referring finally to FIGS. 5 to 7, there is shown another mastercylinder 59 which is provided with an axially parallel recess or cutout59a. The cylinder 59 is mounted on a shaft 58 which also carries acylindrical core 60 performing the function of drums S1, 53 shown inFIG. 4. The core 60 is mounted on the shaft 58 and is provided with twoaxially parallel clamping devices 61, 62 for a foil 7". The clampingdevices 61, 62 are accessible through the cutout 59a when the core 60 isrotated (by a suitable handgrip means, not shown) to assuem the angularposition shown in FIG. 5. One edge portion of the wiping sheet 7b" isthen attached to the clamping device 61 and the core 60 is rotatedthrough a full revolution in a direction indicated by the arrow B. Thismoves the sheet 7b into the annular clearance or gap between thecylinder 59 and drum 6o so that the sheet 7b" is fully concealed whereasthe master sheet 7a remains exposed and can be wrapped around theperiphery of the cylinder 59 (see the arrow C in FIG. S). Once the freeedge portion of the master sheet 7a is attached to the clamping device62, the master cylinder 59 assumes the position shown in FIG. 6y and themaster sheet 7a is ready to transfer an image to the non-illustratedblanket.

Prior to wiping of the blanket, the core 60 is rotated in the directionindicated by the arrow D (see FIG. 7) whereby the clamping device 62retracts the master sheet 7a" into the annular gap between the parts 59,60 and exposes the wiping sheet 7b so that the latter is ready to wipeolf ink from the exposed surface of the blanket. It will be seen thatthe solution shown in FIGS. 5 to 7 is analogous to the solution of FIG.4, i.e., the master cylinder 52 or 59 is provided with means (51, 53 or60) flr selectively concealing the master sheet or the wiping s eet.

In order to convolute the master sheet 7a of FIG. 5 onto the exposedsurface of the master cylinder 59, the cylinder 59 and the core 60 maybe rotated as a unit in a counterclockwise direction. A very importantadvantage 0f the structure shown in FIGS. 5 to 7 is that the core 60 maybe equipped with conventional clamping devices. Furthermore, a singlerevolution of the core 60 with reference to the cylinder S9, or viceversa, suffices to expose the sheet 7a" or 7b. Therefore, such core canbe readily coupled to a rather simple control device (not shown) whichautomatically exposes the wiping sheet 7b" when the printing operationis completed and which can automatically retract the wiping sheet whenthe printing operation begins. Such a control device can turn the core60 with reference to the cylinder 59 while the offset printing machineis in actual use.

The foil 7, 7 or 7 is preferably dirnensioned in such a way that thearea of the master sheet 7a, 7a' or 7a" at least approximates the areaof the wiping sheet 7b, 7b or 7b. The two sheets can be separated fromeach other by a fold 7c shown, for example, in FIG. 4. The freetransverse edge portions of the sheets 7a, 7b or 7a', '7b' or 7a, 7b arepreferably provided with anchoring means to facilitate their attachmentto suitable clamping devices. The anchoring means may be constituted byopenings provided in such edge portions or each such edge portion may bethickened or otherwise reinforced by a rib or bead to be readily held bya conventional clamping device.

The foil 7, 7' or 7" may be made of a single piece of paper or syntheticplastic so that the two sheets 7a, 7b or 7a', 7b or 7a", 7b form anintegral unit. That portion of such integral unit which constitutes themaster sheets (7a, '7a' or 7a") is provided with one or more coats of amaterial adapted to receive ink from the inking roller or rollers 21.

Alternatively, the foil may be assembled of two separate sheets whichare bonded to each other, for example, by adhesive, by welding, byriveting or in another suitable way. That portion of such composite foilwhich constitutes the master sheet may be made up of surface-treatedaluminum, plastic sheet stock or paper. The other portion whichconstitutes the wiping sheet may be made up mainly of roughenedsynthetic plastic stock, roughened textile, absorbent textile, paper orother suitable sheet material.

The provision of a one-piece (composite or integral) foil 7, 7 or 7" hasbeen found to be of considerable advantage because it can be readilyattached to a cylinder 4, 52 or 59 by resorting to a single pair ofclamping devices 5, 6 or 51, 53 or 6l, 62. Of course, and as shown inFIG. 3, it is equally possible to utilize a tirst set of clampingdevices 65, 66 for the wiping sheet 67 and to utilize a second set ofclamping devices to secure the master sheet (not shown) to the mastercylinder of the machine illustrated in FIG. 3.

The improved foil may be produced at low cost in any desired size orshape so that it can be readily fitted on different types of offsetprinting machines. Its edges can be retained by resorting toconventional clamping devices. In fact, a single clamping device maysuce to clamp both edge portions of a foil in an offset printingmachine. If the image on the master sheet 7a, 7a or 7a is formed in atypewriter, the foil 7, 7 or 7 is folded in half so that the wipingsheet 7b, 7b' or 7b" is located behind the master sheet and provides ahigly satisfactory back support during typing. In fact, and since thewiping sheet is often of substantially felt-like consistency, it servesas an exceptionally satisfactory back support which insures that theoutline of each character or symbol is impressed into the master sheetwith unexpectedly satisfactory accuracy.

A foil wherein the two sheets form an integral unit made of a singlesheet of paper or plastic is Often preferred in the production of arelatively small number of copies, for example, in an office. As statedbefore, that portion of the foil which is to form the master sheet iscoated and otherwise treated to be capable of taking ink and oftransferring images to the rubber blanket cylinder. The other portionwhich is to constitute the wiping sheet remains roughened so that it canreadily remove ink from the blanket cylinder. Foils of plastic are oftenpreferred because they do not leave any bres on the surface of theblanket cylinder.

It is also within the scope of my invention to provide the machine withan automatic, semiautomatic or manually operable sprinkling ormoistening device which applies a suitable cleaning liquid onto thewiping sheet 7b, 67, 7b' or 7b after each contact with the blanketcylinder or at less frequent intervals. If provided, such a moisteningdevice constitutes an optional feature of the machine because thematerial of the wiping sheet can be readily selected in such a way thatthe latter can remove from the blanket all traces of ink without theassistance from a special cleaning medium.

What is claimed as new and desired to be protected by Letters Patent is:

1. In an offset printing machine, a rotary rubber blanket cylinder; arotary master cylinder and platen unit for respectively transferring inkimages to and for constituting a back support for said blanket cylinder,said unit comprising a sin gle cylinder; an image transferring mastersheet; a wiping sheet for removing ink from said blanket cylinder, saidsheets together forming a single foil which surrounds the periphery ofsaid single cylinder; and clamping means detachably securing said foilto said unit, comprising two clamping devices associated with saidsingle cylinder.

2. A structure as set forth in claim 1, wherein the length of said foiland the combined width of said clamping devices together approximate thecircumferential length of said single cylinder.

3. A structure as set forth in claim 1, wherein the diameter of saidblanket cylinder approximates half the diameter of said single cylinderand wherein said wiping sheet rolls along and constitutes a back supportfor said blanket cylinder subsequent to transfer of an image onto theexposed surface of said blanket cylinder by said master sheet.

4. A structure as set forth in claim 3, further comprisin inking meansinluding an inking roller movable toward and away from said foil, holdermeans for moving said blanket cylinder toward and away from said foil,and control means including carrier means for moving said inking rolleragainst said master sheet in response to rotation of said singlecylinder and selector means for moving said blanket cylinder against oneof said sheets.

5. A structure as set forth in Claim 4, wherein said selector meanscomprises a selector m-ember movable between a plurality of positions inone of which said blanket cylinder engages only with said master sheetand in another of which said blanket cylinder engages only with saidwiping sheet.

6. A structure as set forth in claim 5, further comprising a feed forsupplying fresh copy sheets into the bite between said blanket cylinderand said single cylinder, said control means including a device foroperating said feed and said selector member being movable to a thirdposition in which said feed is operative and said blanket cylindercontinuously bears against said foil.

7. A structure as set forth in claim 5, wherein said selector member ismovable to a further position in which it maintains said blanketcylinder away from both sheets of said foil.

8. A structure as set forth in claim 5, wherein said control meansfurther comprises a cam provided on said single cylinder and having twoportions respectively associated with said master sheet and said wipingsheet, a rockable motion transmitting lever having a follower arrangedto track said cam portions in response to rotation of said singlecylinder and to thereby rock said lever, said lever having a pluralityof cam faces, and a regulating member coupled with said holder means andmovable by said selector member into and from engagement with selectedcam faces on said lever to thereby determine the position of saidblanket cylinder with reference to said single cylinder.

9. A structure as set forth in claim 8, further comprising a feed forsupplying clean copy sheets into the bite between said blanket cylinderand said single cylinder, said feed being coupled with said selectormember and being arranged to terminate the supplying of copy sheets whensaid selector member is moved to a position in which said regulatingmember is disengaged from said cam faces.

10. A structure as set forth in claim 8, wherein said lever is providedwith three cam faces and is pivotable about a fixed pivot axis, two ofsaid cam faces being disposed at the opposite sides of said axis and thethird cam face being located between said two cam faces.

11. A structure as set forth in claim 1, wherein said single cylindercomprises two portions having different radii, one 0f said portionsbeing surrounded by said master sheet and the other of said portionsbeing surrounded by said wiping sheet.

12. A structure as set forth in claim 11, further comprising a pair ofnormally meshing gears, one of said geais being coaxial with and havingthe same pitch diameter as the diameter of said blanket cylinder, theother of said gears being coaxial with said single cylinder and havingthe same pitch radius as the radius of said one portion.

13. A structure as set forth in claim 1, further comprising a drive forsaid blanket cylinder and clutch means for selectively coupling saidsingle cylinder with said drive.

14. A structure as set forth in claim 13, further comprising manuallyoperated means for manipulating Said clutch means.

15. A structure as set forth in claim 1, wherein said single cylinder ishollow and said clamping devices are provided in the interior of saidsingle cylinder.

16. A structure as set forth in claim 15, wherein each of said clampingdevices comprises a reel for respectively collecting or paying out oneof said sheets.

17. A structure as set forth in claim 16, wherein the length of saidfoil exceeds the circumferential length of said single cylinder.

18. A structure as set forth in claim 15, further comprising a corerotatably received in said single cylinder, said clamping devices beingprovided on said core an said single cylinder having a cutout throughwhich portions of said sheets extend, one of said sheets beingwithdrawable into said single cylinder in response to angulardisplacement of said core in one direction and the other of said sheetsbeing Withdrawable into said single cylinder in response to angulardisplacement of said core in the other direction.

References Cited ROBERT E. PULFREY, Primary Examiner I. REED FISHER,Assistant Examiner U.S. Cl. X.R. lOl-232, 351, 425

